In U.S. Pat. Nos. 3,662,411; 3,789,440; and 4,004,304, there are shown spring assemblies comprising a base frame and a grid frame between which are interposed and to which are connected coiled spring modules. The upper ends of the coiled spring modules are locked to the grid wires of the grid frame by interengagement or deviations in the upper ends of the coils with deviations in the grid wires. As thus structured, manufacture requires two separate operations, to wit, forming deviations in the grid wires and forming deviations in the upper ends of the coils. It is the purpose of this invention to provide means for locking the upper ends of the coils to the grid wires without the need for forming deviations in the grid wires as shown in the aforesaid patents.